Annexation requires two things: 1. Effective control over the territory. 2. The extension of a states domestic laws unto the said territory. Israel has done this to East Jerusalem (though I am uncertain but doubtful that any special arrangements have been made for territory allegedly past the fence. Therefore, Israel has met the two legal requirements of annexation. As to whether or not the territory was up for annexation in the first place, it clear was as East Jerusalem was Terra Nullius when conquered by Israel in 1967. Please note, of course, that the 4th Geneva Convention does not apply to non-state entities as is made clear from the context of the various conferences that went in to the framing of the convention. No amount of international judicial activism can change what was clearly documented regarding the 4th Geneva Convention.
Woman moderately wounded by firebomb thrown at her car in north J'lem (Haaretz)
from the article: Israel bans Palestinian PM from East Jerusalem event